Portions of this invention were made with Government support under Government Contract No. MDA 97294-30028 awarded by DARPA. The Government has certain rights in this invention.
1. Field of the Invention
The field of the invention is imaging or display arrays having address transmission lines, i.e., scan and data transmission lines, and more particularly, to a process for repairing transmission lines that become damaged during the fabrication process of the imager or display arrays.
2. Background
Solid state radiation imagers are commonly formed on a substantially flat substrate, typically glass, and comprise an array of pixels that are used for generating an electrical signal corresponding to the incident radiation. Each pixel includes a photosensitive element, typically a photodiode, and an associated switching element, preferably a field-effect transistor (FET). The array of pixels is typically arranged in a row-column matrix, with each pixel addressed by two electrical transmission lines, a scan transmission line and a data transmission line. The scan lines are typically oriented along rows of the pixel array and coupled to the gate electrode of pixel in that row, with signals applied to the scan lines determining whether the FET is in a conductive or non-conductive state. Data lines are typically oriented along columns of the pixel array and are coupled to source electrodes of the respective pixel FETS in that column, and are used to transfer the electrical signal (corresponding to the charge accumulated on the photosensor during a period of radiation exposure) to readout electronics coupled to the array. The photosensor is further coupled to a common electrode, which electrically connects one contact of the photodiodes in parallel. In various embodiments, the common electrode comprises molybdenum, and in other embodiments the common electrode comprises a layer of indium tin oxide (ITO) which overlays the pixel array.
The operability of the imagers is dependent upon the electrical integrity of the data transmission lines to provide necessary low noise contact to each photosensor to which it is coupled. More particularly, the data transmission lines need to be functional after the completion of all the processing steps for fabricating the imager. However, damage to these transmission lines may occur during processing steps in forming the various components of the imager, such as deposition and patterning of layers of conductive, semiconductive, and dielectric materials to form the photodiodes and FETS and coupled them together in the pixel array. Damaged data lines having open circuit condition render can render significant portions or an entire column of pixels inoperative. A repair process for reestablishing electrical integrity in a severed or damaged data transmission lines is thus helpful to enhance imager performance and increase yield in the fabrication process.
A process for repairing data transmission lines that may have become severed or damaged during the processing steps of the imager desirably is a simple process so as not to unduly degrade the efficiency of the imager fabrication processes and that the integrity of the repair be verifiable in a quick and convenient manner. It also desirable that the have sufficient electrical integrity to provide reliable low noise electrical contact along the data line to maintain imager performance characteristics.